Compressed natural gas (CNG) fuel delivery systems for use in motor vehicles powered by internal combustion engines are generally well-known in the art. More recently, such systems have been combined with gasoline fuel delivery systems to provide so-called dual fuel systems. Such dual fuel motor vehicles are equipped with a multi-fuel engine capable of running on either of CNG and gasoline fuel. In most such systems, the engine is primarily or alternatively fueled by a quantity of CNG stored onboard the vehicle in one or more pressured storage tanks or fuel cylinders. Since the CNG is stored at pressures of about 3000 psi, it is necessary to employ a gas pressure regulator to reduce the pressure of the CNG in the storage tanks from 3000 psi to 30 psi in two stages, from 3000 psi to 80 psi, and then from 80 psi to 30 psi, for delivery to the engine. After this pressure reduction, the CNG is approximately at the same pressure as that provided by gasoline fuel pumps before the fuel is injected into the engine cylinder via the manifold injection system. Thus, the same engine can beneficially use either fuel source, depending on availability.
In most CNG systems, fuel refueling fittings are provided, such as in the engine compartment, by which the pressured storage tanks may be refilled at a refueling station. The pressured storage tanks are in fluid communication with the engine via the gas pressure regulator and an injector assembly, the injector assembly forming a portion of the fuel intake system of the engine. Thus, inlet and outlet CNG lines to and from the gas pressure regulator are required. Since gases cool as they expand, supply and return coolant lines may also be provided to the gas pressure regulator to supply heat to the CNG flowing therethrough and thereby improve combustion by increasing the enthalpy of the fuel delivered to the engine. Accordingly, gas pressure regulators for CNG systems used in motor vehicles are required to have several fittings thereto, many of which create a potential source of leakage of a combustible gas if damaged.
To this end, various regulations and standards have been developed to address the integrity of CNG systems in the event of a collision. One such standard is Federal Motor Vehicle Safety Standard (FMVSS) 303, established by the United States Department of Transportation, National Highway Traffic Safety Admission, which specifies performance requirements for the integrity of motor vehicle fuel systems using CNG. Under FMVSS 303, the CNG system must be able to withstand a 30 mph frontal impact, such that the pressure drop in the high pressure portion of the fuel system, including the storage tanks and gas pressure regulator, does not exceed 154 psi over a 60 minute period following cessation of vehicle motion.
An additional concern of dual fuel motor vehicles lies in packaging the alternative fuel components without changing the gasoline fuel delivery system, which is often a preexisting system. A dual fuel motor vehicle modified to operate with CNG as well as gasoline fuel thus requires a modified engine provided with injectors and combustion cylinders adapted for CNG use, as well as high and low pressure CNG lines, filler nozzle and lines, the pressure regulator, high-pressure storage tanks and an alternative fuel control module as the main components. As a result, scores of additional components and parts are added to such dual fuel vehicles, making the packaging of the new components a challenge.
As noted above, the gas pressure regulator is required to reduce the pressure of the CNG gas in the storage tanks from 3000 psi to 30 psi. Such gas pressure regulators can have an approximate volume of over 2400 cubic centimeters. Thus, due to their relatively large size and complexity, such gas pressure regulators create special packaging concerns in view of the always-present need to balance ease of assembly, serviceability, and protection that arise in every location selection opportunity. Hence, a mounting assembly for a gas pressure regulator that addresses these concerns would be advantageous.
The CNG pressure regulator protective bracket disclosed herein particularly accomplishes the foregoing by providing structure about the gas pressure regulator that encases essentially the entire gas pressure regulator, while simultaneously providing access to the various fittings allowing fluid communication to and from the gas pressure regulator. The present protective bracket itself utilizes a light-weight structure so as not to degrade vehicle efficiency and fuel economy. It also takes advantage of existing structural configurations in order to provide additional protection, and is preferably combined with the vehicle battery tray mounted in front of the gas pressure regulator. The battery and battery tray add structural support and integrity to the protective bracket.
Thus, the solution presented by the present gas pressuring regulator protective bracket is a relatively low-cost, light-weight structure that protects the gas pressure regulator and its associated fittings.